This invention relates to cord winding devices and more particularly to carriage returns on printers or typewriters.
Moving paper carriage printers and typewriters have, in the past, utilized carriage returns in the form of power driven cord reels or tape drums depending on the force transmission member chosen. Patents which deal with the release or the termination of operation of the carriage return drive mechanism include U.S. Pat. Nos. 909,539 to Burlingame, 1,386,387 to Waldheim, 2,647,609 to Sagner and 3,263,793 to Brignole, Jr. U.S. Pat. No. 909,539 is exemplary of a device where the electrical motor power for the carriage return mechanism is interrupted by a mechanical movement caused by the engagement of the left margin stop on the carriage with a follower to effectively break the electrical circuit.
Waldheim discloses a device which is tension governed such that upon the completion of the carriage return movement, the cord tension overcomes spring forces sufficient to pull an electrical switch contact apart, thus preventing further driving by the electrical motor.
Sagner, U.S. Pat. No. 2,647,609, utilizes a mechanical stop member as does Brignole, Jr., 3,263,793, to disengage the driving clutches as a result of the engagement of a knock-off latch by a carriage return stop.
With the exception of the Waldheim reference, all three other references require the carriage return to be returned to the leftmost position on the print line to engage the margin stop with the knock-off mechanism. This requires a complete carriage return and does not allow for carriage jams or other inadvertent blocking of the carriage return and could then cause a burning of the clutch, overloading of the motor, or a breakage of parts. Waldheim permits the disengagement of the motor upon the overcoming of the spring tensions by the carriage return tape. The Waldheim device will, of necessity, require sufficient spring tensions in the spring holding the switch closed to prevent a premature disconnection of the motor contacts. This will, of course, accommodate high initial cord tension and also very high cord tensions in order to accomplish the disconnecting of the motor upon the completion of the carriage return.
All of the above references would require a very substantially sized motor in order to overcome the acceleration forces during the initial phase of carriage return and generate adequate forces to terminate carriage drive.